In recent years, there have been proposed two types of fuel injection devices one of which is adapted to directly inject fuel into a cylinder, and the other of which is designed to jointly use the methods of directly injecting the fuel into the cylinder and injecting the fuel into an intake port.
From the point of view it is necessary to pressurize the fuel to the high pressure and supply the fuel to a fuel injection valve (injector) used for injecting the fuel into the cylinder, there has so far been employed a fuel supply system that supplies the fuel at the high pressure which is produced by even further pressurizing the fuel with the help of a fuel pump used for pressuring the fuel from a feed pump.
As the fuel pump for use in supplying the fuel at the high pressure and the fuel supply system of this kind, there have so far been employed many kinds of fuel pumps and fuel supply systems each of which comprises a pump body (pump housing), a pressurizing plunger mounted on the pump body to be reciprocatable with respect to the pump body, and a pump drive cam driven by the rotational force of the internal combustion engine to reciprocate the plunger. The high pressurized fuel pump thus constructed has a fuel accommodation unit with a damper and capable of intermittently sucking the fuel by the reciprocation motions of the plunger. There have so far been also proposed many types of fuel pumps each of which comprises an auxiliary chamber variable in volume in response to the reciprocation motions of the plunger, and a fuel galley chamber held in communication with the auxiliary chamber.
More concretely, for example known is an apparatus which comprises a pump body having an upper portion formed with a fuel galley formed in a cylindrical shape. The pump body has a lower wall portion forming an inner bottom surface of the fuel gallery chamber and formed with an inlet opening through which the fuel is introduced into the fuel gallery (see for example Patent Document 1).
Further, another known apparatus comprises a pressure adjustment valve capable of adjusting the fuel supply pressure from a low pressure pump to a high pressure pump and the back pressure of the high pressure pump, and a pressure control valve capable of adjusting the discharge pressure of the high pressure pump to a preliminarily set delivery pressure. The relief set pressure of the pressure control valve is set to have a value equal to or larger than a saturated steam pressure corresponding to the maximum temperature of the internal combustion engine after the stoppage of the internal combustion engine (see for example Patent Document 2).
Furthermore, still another known apparatus is proposed to enhance fuel introduction efficiency, and formed with a fuel gallery allowing a lateral flow to be formed toward a suction opening to a pressure chamber side by the fuel introduced through an inlet opening and the fuel introduced from an auxiliary chamber when a plunger is retracted. The suction direction of the fuel from the suction opening to the pressure chamber side is set at an acute angle with respect to the lateral flow (see for example Patent Document 3).